Although expendable thermoplastic packaging is preferred by suppliers and consumers alike for many applications, many people are now concerned over the disposal of such packaging as landfill space becomes increasingly scarce. Packaging materials and containers make up approximately 30 percent of our municipal solid waste stream with packaging produced from thermoplastics accounting for approximately 13 percent of those packaging materials and containers. Greater emphasis is now being placed on the recycling of packaging materials as an important means of reducing our solid waste load.
A significant economical problem exists in the collection of plastic packaging of low bulk density. For example, the typical blow-molded one gallon milk bottle produced from high density polyethylene (HDPE) weighs only 60 grams yet occupies a volume in excess of 230 cubic inches. This equates to a bulk density on the order of less than 1 lb/ft.sup.3, whereas HDPE in solid block form has a density of approximately 60 lbs/ft.sup.3. This difference is even more pronounced for packaging produced from foamed polystyrene where container bulk densities on the order of 0.25 lb/ft.sup.3 are typical even though the density of the polystyrene in solid block form is approximately the same as that of HDPE. Newly made foamed polystyrene food containers nested in stacks weigh about 4 to 6 lbs/ft.sup.3 which is as dense as the product can be made without destroying its intended use. It is difficult to get discarded material this dense even with some compaction. As such, it is generally not economically feasible for the recycler to pick up discarded containers from consumers or businesses without some form of incentive to do so. The plastic food packaging that often contains food residue poses further problems.
The landfill disposal of thermoplastic packaging is also impacted to some extent by low bulk density. Although the problem at the landfill is certainly lessened by the fact that the thermoplastic articles are greatly compacted by the weight of compacting equipment and of subsequently disposed loads, they contribute to the volume of waste in the landfills and add to the cost of collecting and hauling such articles to the disposal site.
An industry which has seen a rapid increase in the use of thermoplastic packaging is the fast-food industry. Thermoplastic packaging offers many highly desirable characteristics and good economic value. Foamed polystyrene is used to form serving trays, hot drink cups, sandwich containers, containers for segregated hot and cold food, and compartmentalized hot food containers. A typical fast-food restaurant may use approximately 20 pounds of foamed polystyrene packaging per day. This small weight is still noteworthy given the fact that the typical sandwich container weighs less than 6 grams or approximately 1/100 of a pound. Even if it is assumed that one-half of this packaging material is taken off the premises of the restaurant in the form of carry-out items, a significant bulk volume of material (an equivalent of more than 750 sandwich containers) is left on site for disposal by the restaurant each day. Although the volume of material that must be handled in this case is quite large, the weight of recoverable polystyrene material is exceedingly small. If such a restaurant were to sell its recovered thermoplastic material to a recycler, the cost of collecting and transporting this material could easily exceed its value.
An added problem is that much of the post-consumer thermoplastic containers have residual food waste present on their inner walls. Without very quick collection and recycling, bacterial activity can present a health problem. This complicates the collection process at many locations where very low tonnage is discarded each day. The shear volume due to the low bulk density and the need to move the material to avoid health and safety issues make accumulating economical amounts for recycling prohibitive.
Another problem area is the disposal of thermoplastic waste at sea. At sea, waste materials are often collected and disposed of by dumping overboard. While much of the waste will decompose with time, or sink to the bottom of the sea, thermoplastic packaging materials generally do neither and eventually wash up on shore. The problems associated with collecting and storing low bulk density material at sea are more acute because of the limited space available for such tasks.
Therefore what is needed to address the disposal problems associated with thermoplastic packaging and containers of low bulk density is an apparatus and method for densifying these discarded thermoplastic articles and for rendering any food remains on these articles bacterially inert.